In recent years, a precision press-molding process (also called mold optics method) attracts attention as a process in which optical elements such as aspherical lenses, etc., formed of a highly functional glass having high refractivity and low dispersion properties or high refractivity and high dispersion properties, can be stably supplied at a low cost in large quantity.
In the precision press-molding method, an optical glass having the low-temperature softening property of being moldable at a relatively low press temperature is used for decreasing damage of a press mold and a mold release film provided on the molding surface of the press mold and for increasing the lifetime of the press mold that is expensive. Such a glass contains Li2O, which is introduced as a glass component for decreasing the glass transition temperature and sag temperature as is disclosed in JP-A-2002-362938.
Meanwhile, when the above glass is precision press-molded, an altered layer called fogging or browning is liable to be generated on the surface of a precision press-molded product. When such fogging or browning exists on a lens surface, or the like, the product is defective, so that it is required to remove a fogged or browned surface by polishing. However, if it is required to apply polishing to the lens surface, etc., of the precision press-molded product for removing the fogging or browning, no features of the precision press-molding method can be utilized.